1. Field of the Invention
This invention relates to an active energy ray-curable composition and a method for using the same to enhance the mechanical strength of glass.
2. Prior Art
Two methods to enhance the mechanical strength of glass containers are disclosed by Unexamined Japanese Patent Publication No. 1-201047; (1) A glass surface is treated with a silane coupling agent, coated with a curable composition containing one or more types of curable compounds that have, in their molecular structure, two or more acryloyl groups selected from a fluoroacryloyl, methacyloyol or acryloyl group, and cured with active energy ray, and (2) A glass surface is coated with the aforementioned curable composition containing a silane coupling agent and is then cured with active energy ray. In the following description, acryloyl, methacryloyl and fluoroacryloyl are referred to as (meth)acryloyl, and acrylate, methacrylate and fluoroacrylate are referred to as (meth)acrylate.
Method (1), which has one more processing step, offers less productivity than Method (2). On the other hand, the active energy ray-curable composition of Method (2), consisting of an active energy ray-curable compound, a silane coupling agent and an organic solvent, is unstable; as a result, in that the maximum original strength rendered by the fresh composition can hardly be expected from a composition stored for a long time, or the composition can be expected to only slightly improve the mechanical strength of the glass container over which it is spread when it is used after being after being stored for a long time.
The applicants of the present invention have investigated how to develop a curable composition which enhances the mechanical strength of a glass container, even after being stored for a long time, to the maximum extent that a fresh composition does, and have found that the curable composition of Method (2) can have unexpectedly high storage stability when mixed with water. In such a way the mechanical strength of the glass container can be guaranteed to the same extent as when using a fresh composition, even if the composition has been stored for a long time.